1. Field of the Invention
The present invention relates to an apparatus for testing and monitoring of electric heaters, and, more particularly, to an apparatus for testing and monitoring of electric heaters used to melt and thus remove snow and ice from pavement, roofs, gutters, down spouts, satellite dishes and the like.
2. Description of the Related Art
Electric heaters may be utilized to supply heat used in snow and ice melting systems. Typical melting applications include but are not limited to satellite dishes, roofs and gutters, pavement, building and garage entrances and facilities accommodating the physically challenged. Efficient operation requires embedding the electric heaters in or attaching the electric heaters to satellite dishes, pavement and other structures which may sometimes become covered with snow and ice.
Snow and ice melting systems commonly employ automatic ON/OFF controls that operate heaters only while required to minimize energy consumption and operating costs. Typically, the automatic ON/OFF controls sense ambient moisture and temperature. However, it is also possible for the automatic ON/OFF control to be in the form of a thermostat which only senses ambient temperature. Heaters operate at ambient temperatures below a threshold--usually 38.degree. F. while ambient moisture is present and for a period of time thereafter to clear accumulated snow and ice. Optionally, the automatic ON/OFF control may inhibit heater operation at temperatures too low for effective melting, e.g., below 17.degree. F. Status indicators and a manual control and test switch are typically included in the same package with such automatic ON/OFF controls.
In order to reduce costs and simplify installation, it is known to attach the automatic ON/OFF control package to the support structure of a satellite dish antenna, or "reflector". A problem with attaching the control package to the support structure of a reflector is that it requires access to the reflector in order to observe the status indicators and to test deicing system performance with the manual control and test switch. Since the reflector must be placed within the line of sight of the associated satellite for reliable communications, the reflector must almost always be placed at an elevated location, such as on a rooftop or a pole. Thus, nearly all antenna locations are not easily accessible for purposes of observing and testing deicing system performance.
In a known method of attaching the control package to the support structure of a reflector, a hole is drilled in a support arm thereof. Using the drilled hole, a bracket is bolted to the support arm of the reflector, and the control package is attached to the bracket. A problem is that this is a cumbersome process that requires specialized tools.
Moreover, in many retail applications, frequent relocation of the reflector is required. While the reflector itself is typically not relocated because it would not be cost effective to do so, it is cost effective to transfer the automatic ON/OFF control package along with the associated wiring to the new reflector location. A problem is that the cumbersome process of attaching the control package must be repeated at the new reflector location. An additional problem is that the bolt securing the control package to the first reflector may be rusty from exposure to the elements, making its removal extremely difficult.
Ground current is the difference between the outbound and return heater currents. The U.S. National Electric Code requires using a ground fault circuit interrupter (GFCI) on all snow and ice melting circuits. The GFCI interrupts heater current if the ground current exceeds a predetermined limit; usually 30 milliamperes. The GFCI requires manual reset after tripping. This preserves safety by not restarting heater operation during intermittent ground leakage current that may occur in wet locations.
Independent of the heater fabrication method, ground current can flow due to a heater failure caused by a manufacturing defect, corrosion, wear and tear or mechanical damage. Excessive ground current causes the dual safety problems of fire and shock hazard. An electrical shock hazard can also occur whenever ground current flows since its path to earth ground is usually not predictable. Thus, a GFCI is required to be incorporated into snow and ice melting electrical circuits. It is known to install a residential GFCI in a knockout box convenient to the deicing system. A problem is that this task must be performed by an electrician, thereby adding to the cost of transferring the heater circuitry when a new reflector location is needed.
Until recently, reflectors have almost always measured at least 1.8 meters across for very small aperture terminal (VSAT) applications. These 1.8 meter reflectors require over 650 watts of deicing power, which is enough to justify the cost of automatic ON/OFF controls in most climates. Due to improvements in ground and space equipment, smaller antennas measuring no more than 1.2 meters across have become practical. These 1.2 meter reflectors require only approximately 250 watts of deicing power for the lower half of the reflector, which is not enough to justify the cost of automatic ON/OFF controls in most climates. Nevertheless, automatic ON/OFF controls are almost universally used with 1.2 meter reflectors because of the desirability of the status indicators and the manual control and test switch that are included in the same package as the automatic ON/OFF controls. Thus, a problem is that automatic ON/OFF controls are often used in applications in which their cost is not warranted.
What is needed in the art is a device for testing and monitoring the operation of a reflector deicing system that is conveniently accessible to operating personnel, can be easily transferred between reflector locations, and which does not require the use of expensive automatic ON/OFF controls.